The present invention relates to display panels of the type known as SELF-SCAN panels. Panels of this type are shown in U.S. Pat. No. 3,989,981 and 3,995,185, which are incorporated herein by reference. These panels include between the base plate and face plate a cell sheet made of Fotoform glass which is a photosensitive glass which is described in U.S. Pat. Nos. 2,971,853, 2,684,911, and 2,628,160. Briefly, Fotoform sheets are made by preparing a particular glass composition in the desired shape and processing to form a clear sheet which is photosensitive. The sheet is photographically exposed and etched to provide cells or slots, as required, and then it is further processed to render it opaque, a requirement for some display devices. It has been observed that Fotoform cell sheets thus processed do not have uniform thickness and the top and bottom surfaces are not uniformly spaced apart throughout the area of the sheet. Such dimensional nonuniformity is detrimental to proper construction and operation of display panels, especially display panels known as SELF-SCAN II panels.
The present invention provides a display panel having a cell sheet which is opaque, has dimensional uniformity, and is relatively inexpensive and easy to manufacture. Briefly, the invention comprises preparing a plate of photosensitive insulating material and photographically exposing and etching to form a plate having the desired pattern of openings. The plate thus formed is not processed to its opaque state, but rather, it is coated with silicon to form a thin coating which is opaque and highly resistive, as desired.